The disclosure of Japanese Patent Application No. 2000-226654 filed on Jul. 27, 2000, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a torque fluctuation absorbing apparatus having a structure for reducing misalignment of a torque limiter during assembling of the apparatus, and also relates to a method for assembling the torque fluctuation absorbing apparatus while reducing misalignment of the torque limiter when it is mounted in the apparatus.
2. Description of Related Art
A torque fluctuation absorbing apparatus is coupled to and between an engine crankshaft and an input shaft of a driven-side assembly (e.g., a transmission of a hybrid vehicle which houses a motor) so as to reduce engine torque fluctuations.
FIG. 9 and FIG. 10 show a known example of torque fluctuation absorbing apparatus. The torque fluctuation absorbing apparatus 1 includes a flywheel 10 coupled to a crankshaft 2 of an engine, a damper assembly 20 disposed in a torque transmission path between the flywheel 10 and a driven-side input shaft 3, and a torque limiter 30 disposed in a torque transmission path between the flywheel 10 and the damper assembly 20. The damper assembly 20 has a pair of drive plates 21, a driven plate 22, and spring dampers 24. The torque limiter 30 has a pair of linings 31 and a damper cover 32, and is adapted to slip when receiving a predetermined or larger amount of torque.
The pair of linings 31 are secured to both faces of an outer peripheral portion of one of the drive plates 21 (or a member fixed to the drive plate 21). The pair of linings 31 are sandwiched between the damper cover 32 and the flywheel 10. When a torque that is equal to or larger than a predetermined value is applied to the torque limiter 30, slippage occurs on surfaces of the linings 31 that are in contact with the damper cover 32 and the flywheel 10. The drive plates 21 and the driven plate 22 are rotatable relative to each other in a circumferential direction thereof. Also, small amounts of radial clearances are provided between a bush 23 disposed between the drive plate 21 and the driven plate 22, and the drive plates 21 and the driven plate 22, respectively, whereby the drive and driven plates 21, 22 rattle in the radial directions. In order to allow or accommodate rattling and assembling errors, a radial clearance d is provided between an outer periphery of the drive plate 21 (or a member secured thereto) and an inner periphery of the flywheel 10.
A procedure of assembling the known torque fluctuation absorbing apparatus 1 is as follows: (1) a hub 22a of the driven plate 22 of the damper assembly 20 and the crankshaft 2 are aligned with an engine assembly by using a jig 50, as shown in FIG. 10, (2) the damper cover 32 is bolted to the flywheel 10, and the damper cover 32 and the flywheel 10 sandwich the linings 31 secured to the drive plate 21 to thereby support the damper assembly 20, and (3) the engine assembly is assembled with a driven-side assembly, and these assemblies are thus fixed to each other.
The known apparatus, however, has following problems.
In the presence of the radial clearance between the drive plate and the driven plate as described above, the drive plate may be disposed eccentrically within the range of the clearance with respect to the flywheel, even with the driven plate being properly aligned with the engine assembly by using the jig upon assembling of the torque fluctuation absorbing apparatus with the engine assembly. As a result, the linings of the torque limiter secured to the drive plate may be out of alignment with respect to the flywheel in the radial directions. If the torque limiter is assembled eccentrically with the engine assembly, the following and/or other problems may occur when the engine is rotated, after assembling of the engine assembly with the driven-side assembly, to an angular point where the radial clearance between the drive plate and the driven plate disappears. For example, 1) the rotation of the input shaft of the driven-side assembly may become unstable or fluctuating due to the eccentric arrangement of the drive and driven plates, and torsional stress may be applied to a bearing 60 that supports the input shaft of the driven-side assembly, resulting in a reduction in the service life of the bearing 60, 2) the service life of a bushing 61 (or a needle bearing) that is in sliding contact with the driven-side input shaft during rotation thereof may be shortened, and 3) the performance of an oil seal 62 that is in sliding contact with the driven-side input shaft may deteriorate.
It is an object of this invention to provide a structure and a method (an assembling method) for reducing misalignment of a torque limiter during assembling of a torque fluctuation absorbing apparatus.
To accomplish the above and/or other objects, there is provided according to one aspect of the invention a torque fluctuation absorbing apparatus provided between a crankshaft of an engine and a driven-side input shaft, comprising: (1) a flywheel coupled to the crankshaft, (2) a damper assembly disposed in a torque transmission path between the flywheel and the driven-side input shaft, the damper assembly including a pair of drive plates, a driven plate and at least one spring damper, and (3) a torque limiter disposed in a torque transmission path between the flywheel and the damper assembly, the torque limiter including a pair of linings that are adapted to slip when receiving at least a predetermined amount of torque. In this apparatus, the torque limiter further includes a lining support plate to which the linings are fixed, and the linings are interposed between the pair of the drive plates. In fabricating this apparatus, the drive plates and the linings are centered with each other and assembled into a damper-torque limiter assembly, while the lining support plate is centered with respect to the flywheel, such that the damper-torque limiter assembly is fixed at the lining support plate to the flywheel. With this arrangement, the drive plates, the linings, and the flywheel are brought into concentric relationship with each other, thus effectively preventing the torque limiter from being eccentrically positioned with respect to the engine assembly during assembling of the apparatus.
According to a second aspect of the invention, there is provided a torque fluctuation absorbing apparatus including the flywheel, the damper assembly and the torque limiter as described above, in which the linings of the torque limiter are fixed to one of the drive plates of the damper assembly, and the torque limiter includes a pair of damper covers between which the linings are interposed. In fabricating this apparatus, the drive plates and the damper covers are centered with each other and assembled into a damper-torque limiter assembly, while the damper covers are centered with respect to the flywheel, such that the damper-torque limiter assembly is fixed at the damper covers to the flywheel.
According to a third aspect of the invention, there is provided a torque fluctuation absorbing apparatus including the flywheel, the damper assembly and the torque limiter as described above, in which the linings of the torque limiter are fixed to one of the drive plates, and the linings are interposed between the flywheel and a damper cover that forms a part of the torque limiter, while the flywheel includes a flywheel main body and a flywheel plate that are fastened to each other. In fabricating this apparatus, the drive plates, the linings and the damper cover are centered with respect to the flywheel main body, and are assembled together to provide an assembly of the flywheel main body, the damper assembly and the torque limiter. After the engine is assembled with the drive-side input shaft, the assembly of the flywheel main body, the damper assembly and the torque limiter is fastened to the flywheel plate that is fixed to the crankshaft.
According to a fourth aspect of the invention, there is provided a torque fluctuation absorbing apparatus including the flywheel, the damper assembly and the torque limiter as described above, in which the driven-side input shaft includes an axially protruding portion at a distal end thereof, and the crankshaft has a recess formed in a distal end portion thereof, and a bearing that is fitted in the recess. Furthermore, the axially protruding portion is received in an inner bore of the bearing, and an elastic material is provided between the bearing and the crankshaft or between the bearing and the axially protruding portion.
According to a fifth aspect of the invention, there is provided a torque fluctuation absorbing apparatus including the flywheel, the damper assembly and the torque limiter as described above, and further including a bearing that is fitted in a recess formed in a distal end portion of the crankshaft, and a drive plate support member that supports the drive plates. One end of the drive plate support member is fitted in an inner circumferential wall of the bearing, and the other end of the drive plate support member is fixed to one of the drive plates.
According to a sixth aspect of the invention, there is provided a torque fluctuation absorbing apparatus including the flywheel, the damper assembly and the torque limiter as described above, and further including a bearing that is fitted in a recess formed in a distal end portion of the crankshaft, and a driven plate support member that supports the driven plate. One end of the driven plate support member is fitted in an inner circumferential wall of the bearing, and the other end of the support member is fixed to the driven plate.